CN108114711B

CN108114711B - Transition metal oxide catalyst for catalytic removal of ozone and preparation method thereof

Info

Publication number: CN108114711B
Application number: CN201611090572.9A
Authority: CN
Inventors: 王胜; 张磊; 王树东; 丁亚; 汪明哲
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2016-11-30
Filing date: 2016-11-30
Publication date: 2021-07-16
Anticipated expiration: 2036-11-30
Also published as: CN108114711A

Abstract

The invention relates to a transition metal oxide catalyst for catalytic removal of ozone and a preparation method thereof, belonging to the field of catalysis and environmental protection. The catalyst is a transition metal oxide MO_xThe active component is the transition metal M, wherein x is 0.5-2.5, and the transition metal M is one or a combination of more of Cu, Co, V, Cr, Mn, Fe, Ru, Rh, Pd, Ag, Pt, Au, Ce and La; the transition metal oxide MO is added_xThe catalyst with different structures is prepared by molding or is loaded on an inert carrier with larger specific surface area to prepare the ozone catalytic decomposition catalyst. The method for preparing the catalyst has the advantages of simple process, mild conditions, high ozone decomposition efficiency of the nano fibrous metal oxide and stable performance.

Description

Transition metal oxide catalyst for catalytic removal of ozone and preparation method thereof

Technical Field

The invention belongs to the field of catalysis and environmental protection, and particularly relates to a transition metal oxide catalyst for catalytic removal of ozone and a preparation method thereof.

Background

Ozone is an important trace component of natural atmosphere, is composed of three oxygen atoms, is an allotrope of oxygen, has strong oxidizing property, and is widely applied to the aspects of medical sanitation, chemical oxidation, water pollution treatment and the like. Ozone often produces a large amount of residue during use, and the residue is directly discharged into the atmosphere to cause environmental pollution. In addition, electrical appliances used in daily life of people, such as air purifiers, copiers, etc., also generate ozone during working, resulting in excessively high indoor ozone concentration. In special environments, such as aircraft cabins, the introduction of gases is inevitably accompanied by the entry of the aircraft into the stratosphereOzone, therefore, causes the concentration of ozone in the cabin to increase. High-concentration ozone can cause acute injury to human bodies, stimulate respiratory systems, cause neurotoxicity, destroy immune systems and the like. The maximum concentration allowed in the working environment of 8 hours is regulated to be lower than 160ug/m in environmental air quality standard (GB3095-2012) issued in 2012 of China³。

The current methods for ozonolysis mainly comprise: activated carbon adsorption, solution absorption, thermal decomposition, catalytic decomposition, and the like. The activated carbon adsorption method has high cost because the activated carbon has saturated adsorption and needs frequent regeneration; the solution absorption method has the problem of sewage treatment; the thermal decomposition method requires heating and increases energy consumption, while the catalytic decomposition method is economically and efficiently focused because it can decompose ozone at normal temperature, but the research of the catalyst is difficult.

The active components for the ozonolysis catalyst are mainly of two types: noble metal catalysts and transition metal oxide catalysts. The active components of the noble metal catalyst are mainly Pt, Pd, Ru and the like, but most of research is focused on the transition metal oxide due to high price, small reserves and limited large-scale application of the noble metal. Oyama et Al in supporting various transition metal oxides to Al₂O₃The ozonolysis performance is studied to obtain MnO₂Conclusion of best activity. But due to O₃The decomposition is a redox process, so MnO_xThe mixed valence state of Mn in the structure is more favorable for improving the catalytic activity of Mn. In patent US5296435 MnCO is roasted at high temperature₃A series of products were obtained, and MnO was found to be obtained by baking at 350 ℃_x(x ═ 1.6-2.0) and MnCO₃The ozonolysis activity of the mixture is the best. O is₃The concentration is 15ppm, and the space velocity is 3000h^-1Under the condition that the relative humidity is 80%, the ozone conversion rate can be kept at about 88% at room temperature after 100 hours. Pengyi Zhang et al used hydrothermal method to synthesize MnO with different shapes₂The study found that MnO was in the form of nanofibers₂The catalytic ozonolysis performance is best. Currently in relation to MnO_xThe synthesis of the nano-fiber is carried out by a hydrothermal method, and the preparation conditions are relatively harsh.

Disclosure of Invention

The invention provides a transition metal oxide catalyst for catalyzing and removing ozone and a preparation method thereof, aiming at the defects in the prior art.

A transition metal oxide catalyst for catalytic removal of ozone is prepared from transition metal oxide MO_xThe active component is the transition metal M, wherein x is 0.5-2.5, and the transition metal M is one or a combination of more of Cu, Co, V, Cr, Mn, Fe, Ru, Rh, Pd, Ag, Pt, Au, Ce and La; the transition metal oxide MO is added_xThe catalyst with different structures is prepared by molding or is loaded on an inert carrier with larger specific surface area to prepare the ozone catalytic decomposition catalyst. The catalyst has high ozone decomposition efficiency and stable performance.

A preparation method of a transition metal oxide catalyst for catalytically removing ozone comprises the following steps:

1) transition metal oxide active component MO_xThe preparation of (1): preparing intermediate MOOH by ordinary liquid-phase synthesis method, and preparing MO by regulating roasting temperature and atmosphere_x。

The ozonolysis catalyst of the invention adopts two steps of liquid phase synthesis of an intermediate and high-temperature pyrolysis of the intermediate to prepare the catalyst, and the preparation method comprises the following steps:

dropwise adding 1-50ml of precipitator and oxidant with the molar concentrations of 0.1-1mol/L into 0.1-1.0mol/L of precursor solution of transition metal oxide under the condition of stirring at the speed of 0.04-1ml/min to prepare mixed solution A; then, putting the mixed solution A into a water bath kettle, stirring for 8-24h at 40-60 ℃, washing with deionized water and absolute ethyl alcohol, and vacuum drying for 12h at 60 ℃ to obtain an intermediate B; roasting the intermediate B for 3-6h at the temperature of 600 ℃ in an oxidizing or inert atmosphere to obtain a metal oxide active component MO_x，

(2) The active component MO of transition metal oxide_xTabletting, rolling ball or extrusion molding to obtain catalyst MO_x(x＝0.5-2.5)；

Or a transition metal oxide active component MO_xLoaded onto inerts having a large specific surface areaThe sex carrier is specifically as follows: firstly loaded on the surface of a carrier, and then pyrolyzed at high temperature to prepare MO_xAn inert supported catalyst.

The inert carrier with larger specific surface area is active carbon, active carbon fiber, molecular sieve and other micropore or mesoporous materials.

The precipitant is ammonia gas, ammonia water, ammonium salt, carbon dioxide, carbonate and alkali or urea,

the ammonium salt is ammonium carbonate, ammonium sulfate, ammonium acetate or ammonium oxalate; the carbonate is sodium carbonate or ammonium bicarbonate, and the alkali is sodium hydroxide.

The oxidant is hydrogen peroxide, potassium permanganate, potassium perchlorate, potassium hypochlorite, ozone, oxygen or air.

The precursor of the transition metal oxide is nitrate, carbonate, acetate and other water-soluble salts.

The active component provided by the invention is transition metal oxide MO_xThe catalyst is applied to catalytic removal of ozone, and can also be used for catalytic removal of CO and CH₄And VOCs.

The MO provided by the invention_xCatalysts or MOs_xInert carrier catalyst applied to ozone catalytic removal reaction with reaction space velocity of 10,000-^-1The volume concentration of raw material gas ozone is 0.1-100ppm, the catalyst can realize complete removal of ozone at normal temperature, and has high stability.

The active component of the invention is transition metal oxide MO_xThe catalyst has the following advantages:

1. the active component of the invention is transition metal oxide MO_xThe catalyst has high ozone removal activity and stability under the condition of higher space velocity.

2. The active component of the invention is transition metal oxide MO_xThe catalyst has high catalytic ozone removal activity, and can completely remove ozone at normal temperature.

3. The active component of the invention is transition metal oxide MO_xCatalyst of (1) inHas high stability at normal temperature.

4. The active component of the invention is transition metal oxide MO_xThe catalyst has simple synthesis process and controllable catalyst morphology.

Drawings

FIG. 1 is an SEM photograph of the catalyst of example 1;

figure 2 XRD pattern of the catalyst in example 2;

FIG. 3 is an SEM photograph of the catalyst of example 2;

figure 4 XRD pattern of the catalyst in example 3;

FIG. 5 SEM image of catalyst from example 4.

Detailed description of the preferred embodiments

The following detailed description of the present invention is merely a preferred embodiment of the present invention, and is not intended to limit the scope of the invention. All the equivalent changes and modifications made according to the claims of the present invention should fall within the scope covered by the present invention.

Example 1

Into a 250mL round bottom flask was added 50mL deionized water, followed by Mn (AC)₂To this was added 50mL of a NaOH solution and 20mL of 30% H with stirring₂O₂The solution was added simultaneously to Mn (AC)₂In solution, Mn²⁺With OH^-The molar ratio of the components is 1:2, the solution is changed from colorless transparent solution to black brown turbid solution, after stirring for 20min, the solution is heated to 60 ℃ by adopting a water bath, refluxing is carried out for 12h, suction filtration is carried out, washing is carried out by using deionized water and absolute ethyl alcohol, and finally drying is carried out in a vacuum oven at 60 ℃ for 12 h. Sieving the dried catalyst into particles with the size of 40-60 meshes for later use, wherein the catalyst is in a nano-fiber shape (figure 1). 0.1g of the catalyst was placed in a tubular fixed bed reactor to conduct evaluation of the catalyst.

Example 2

Into a 250mL round bottom flask was added 50mL deionized water, followed by Mn (AC)₂To this was added 50mL of a NaOH solution and 20mL of 30% H with stirring₂O₂The solution was added simultaneously to Mn (AC)₂In solution, Mn²⁺With OH^-The molar ratio of the solution to the organic solvent is 1:2, the solution is changed from colorless transparent solution to black brown turbid solution,stirring for 20min, heating to 60 deg.C in water bath, refluxing for 12 hr, vacuum filtering, washing with deionized water and anhydrous ethanol, and drying in vacuum oven at 60 deg.C for 12 hr. Vacuum drying the obtained product, roasting at 350 ℃ in air atmosphere to obtain MnO₂The XRD pattern is shown in figure 2. And sieving the roasted catalyst into particles with the size of 40-60 meshes for later use. 0.1g of the catalyst was placed in a tubular fixed bed reactor to conduct evaluation of the catalyst.

Example 3

Into a 250mL round bottom flask was added 50mL deionized water, followed by Mn (AC)₂To this was added 50mL of a NaOH solution and 10mL of 30% H with stirring₂O₂The solution was added simultaneously to Mn (AC)₂In solution, Mn²⁺With OH^-The molar ratio of the components is 1:1, the solution is changed from colorless transparent solution to black brown turbid solution, after stirring for 20min, the solution is heated to 60 ℃ by adopting a water bath, refluxing is carried out for 12h, suction filtration is carried out, washing is carried out by using deionized water and absolute ethyl alcohol, and finally drying is carried out in a vacuum oven at 60 ℃ for 12 h. Vacuum drying the obtained product, roasting at 600 ℃ in argon atmosphere to obtain Mn₂O₃The XRD pattern is shown in FIG. 4. And sieving the roasted catalyst into particles with the size of 40-60 meshes for later use. 0.1g of the catalyst was placed in a tubular fixed bed reactor to conduct evaluation of the catalyst.

Example 4

Into a 250mL round bottom flask was added 50mL deionized water, followed by Mn (AC)₂Adding into the solution, adding 1mL of acetic acid under stirring, introducing oxygen for 2mL/min, adding 50mL of NaOH solution into the round bottom flask, adding Mn²⁺With OH^-The molar ratio of the organic solvent to the organic solvent is 1:2, stirring is carried out for 20min, the solution is colorless and transparent and is changed into orange solution, heating is carried out in a water bath to 60 ℃, refluxing is carried out for 12h, the solution is changed into brown turbid solution from orange, suction filtration is carried out, washing is carried out by deionized water and absolute ethyl alcohol, and finally drying is carried out in a vacuum oven at 60 ℃ for 12 h. And sieving the dried catalyst into particles with the size of 40-60 meshes for later use, wherein the appearance of the catalyst is shown in figure 5. 0.1g of the catalyst was placed in a tubular fixed bed reactor to conduct evaluation of the catalyst.

Example 5

A500 mL round bottom flask was charged with 100mL deionized water, and Mn (AC)₂Adding into the solution, adding acetic acid 4mL under stirring, introducing oxygen 2mL/min, adding 100mL of NaOH solution into round bottom flask, adding Mn²⁺With OH^-The molar ratio of the organic solvent to the organic solvent is 1:2, stirring is carried out for 20min, the solution is colorless and transparent and is changed into orange solution, heating is carried out in a water bath to 60 ℃, refluxing is carried out for 12h, the solution is changed into brown turbid solution from orange, suction filtration is carried out, washing is carried out by deionized water and absolute ethyl alcohol, and finally drying is carried out in a vacuum oven at 60 ℃ for 12 h. Vacuum drying the obtained product, and roasting at 300 ℃ in an air atmosphere. The detected product is MnO₂. And sieving the roasted catalyst into particles with the size of 40-60 meshes for later use. 0.1g of the catalyst was placed in a tubular fixed bed reactor to conduct evaluation of the catalyst.

All of the above examples were subjected to performance testing under the following conditions:

normal temperature and normal pressure. Gas composition: 50% of air, 50% of argon, and ozone gas are generated by an ozone generator, argon is blown into a reaction system, the concentration of ozone is controlled to be 10ppm, and the reaction space velocity (GHSV) is

276,000h^-1. The catalyst performance comparisons are shown in table 1.

TABLE 1 comparison of catalyst Performance

Claims

1. The transition metal oxide catalyst for catalytically removing ozone is characterized in that the catalyst is transition metal oxide MO_xIs active component, wherein x =0.5-2.5, transition metal M is Mn and one or more selected from Cu, Co, V, Cr, Fe, Ru, Rh, Pd, Ag, Pt, Au, Ce and La; the transition metal oxide MO is added_xForming to obtain catalysts with different structures or loading the catalysts on an inert carrier with a large specific surface area to obtain an ozone catalytic decomposition catalyst;

the preparation method of the ozone catalytic decomposition catalyst comprises the following steps:

(1) transition metal oxide active component MO_xThe preparation of (1): is divided intoThe method comprises two steps of high-temperature pyrolysis for liquid-phase synthesis of an intermediate, and comprises the following specific steps:

dropwise adding 1-100ml of precipitator with the molar concentration of 0.1-1mol/L and liquid oxidant into 0.1-1.0mol/L of precursor solution of transition metal oxide under the condition of stirring at the speed of 0.04-1ml/min to prepare mixed solution A; for the gaseous oxidant, when the precipitator is dripped, the gaseous oxidant is added into the transition metal oxide precursor by bubbling for 0.1-100 ml/min; wherein the liquid oxidant is hydrogen peroxide, potassium permanganate, potassium perchlorate or potassium hypochlorite; the gaseous oxidant is ozone;

then, the mixed solution A is put into a water bath kettle at 40-60 DEG^oStirring for 8-24h at C, washing with deionized water and anhydrous ethanol, and washing with 60% ethanol^oC, vacuum drying for 12 hours to prepare an intermediate B; the intermediate B is subjected to 300-600 in an oxidizing or inert atmosphere^oRoasting for 3-6h under the condition of C to obtain MO_xA catalyst;

(2) the above transition metal oxide MO is added_xMolding, specifically, preparing the catalyst with a specific geometric structure by tabletting or rolling balls; or the above transition metal oxide MO_xLoading on an inert carrier with a large specific surface area, specifically: impregnating and loading the mixed solution A prepared in the step (1) on the surface of a carrier, and then carrying out high-temperature pyrolysis according to the method in the step (1) to obtain the mixed solution A; the inert carrier with larger specific surface area is active carbon, molecular sieve and other micropore or mesoporous materials.

2. A method for preparing a transition metal oxide catalyst for catalytic removal of ozone according to claim 1, comprising the steps of:

(1) transition metal oxide active component MO_xThe preparation of (1): the method comprises two steps of liquid-phase synthesis of an intermediate and high-temperature pyrolysis, and comprises the following specific steps:

(2) the above transition metal oxide MO is added_xMolding, specifically, preparing the catalyst with a specific geometric structure by tabletting or rolling balls; or the above transition metal oxide MO_xLoading on an inert carrier with a large specific surface area, specifically: loading the mixed solution A prepared in the step (1) on the surface of a carrier, and then carrying out high-temperature pyrolysis according to the method in the step (1) to obtain the mixed solution A; the inert carrier with larger specific surface area is active carbon, molecular sieve and other micropore or mesoporous materials.

3. The method of claim 2, wherein the precipitant is selected from the group consisting of ammonia, ammonium carbonate, ammonium bicarbonate, sodium hydroxide, and urea.

4. The method of claim 2, wherein the precursor of the transition metal oxide is a nitrate or other water-soluble salt thereof.

5. Use of a transition metal oxide catalyst for the catalytic removal of ozone as claimed in claim 1 wherein the catalyst is used for ozone, CO or CH₄Catalytic removal of (3).